Dipeptidyl peptidase IV (DP 4) inhibiting compounds are provided having the formula (I) where x is 0 or 1 and y is 0 or 1 (provided that x = 1 when y = 0 and x = 0 when y = 1)； n is 0 or 1； X is H； and wherein R 1 , R 2 , R 3 and R 4 are as described herein. A method is also provided for treating diabetes and related diseases, especially Type II diabetes, and other diseases as set out herein, employing such DP 4 inhibitor or a combination of such DP 4 inhibitor and one or more of another antidiabetic agent such as metformin, glyburide, troglitazone, pioglitazone, rosiglitazone and/or insulin and/or one or more of a hypolipidemic agent and/or anti-obesity and/or other therapeutic agent.
